1. Field of the Invention
The present invention relates to a apparatus for joining opposite ends of a strip of tread in a machine for making a tire.
2. Description of the Prior Art
Treads are cut to a length each corresponding to the circumference of a tire. The length of such treads may vary depending not only on how accurately they are cut, but also on mixing conditions, the period between an extrusion process and a molding process, and temperature or other conditions. A tolerance of a part of the tire in which opposite ends of each tread is joined is quite small for achieving better performance of the tire.
(1) A conventional apparatus for joining the ends of a tread includes no effective means for altering or adjusting the length of a tread. To this end, an operator must manually adjust it by himself in the process of joining the ends of the tread.
(2) There has been proposed a method for joining opposite ends of a tread by adjusting the speed of each of a conveyor and a tread drum to wrap the tread, as cut to a length equal to the circumference of a tire, around the drum.
(1) As earlier stated, the length of the treads as cut may vary depending not only on how accurately they are cut, but also on mixing conditions, the period between an extrusion process and a molding process, and temperature or other conditions. A tolerance for of a part of the tire in which opposite ends of each tread is joined is however quite small. The manual adjustment of the length of each tread by the operator suffers from the following problems:
a) Considerable skill is required; PA1 b) It is a heavy work; and PA1 c) It is not efficient, and the opposite ends of the tread are not always joined in an accurate fashion.
(2) A disadvantage with the method for joining opposite ends of a tread by adjusting the speed of each of a conveyor and a tread drum, so as to wrap the tread around the drum, is as follows.
As shown in FIG. 15, the speed of a conveyor and a tread drum is adjusted to wrap a tread 57 around the drum in such a manner as to bring the centers E of the front and rear ends of the tread 57 into alignment with each other. In such a case, between any portions of the tread 57 other than at the center E there is likely to be spaces X.sub.1 and X.sub.2. To this end, an operator must manually alter or adjust the rear end of the tread.